The present apparatus is directed to a device which determines the rate of leakage from a liquid impoundment. This apparatus in particular can be used to determine if liquid is being lost out of the liquid impoundment to the surrounding ground. As a matter of background, it is useful in a liquid impoundment which is formed by scooping out a shallow lake or pond and it is particularly noted that this impoundment may or may not be lined with one or more layers of a geomembrane intended to retain such impounded liquids. The impoundment is filled with some liquid. Normally, it is a liquid where leakage is considered highly undesirable. It is very difficult to know whether or not leaking is occurring. One way to know this is to measure and monitor the liquid mass balance between all known inputs and outputs from the impoundment. This is a difficult procedure. The present apparatus enables the determination of whether or not the reservoir is losing liquid, this liquid loss being isolated from liquid losses as a result of surface evaporation. Thus, the present apparatus can be used to determine, if in the first instance, there is a liquid loss to the ground.
Loss of liquid from a liquid impoundment is difficult to know and calculate by virtue of the fact that the bulk of the loss typically will occur through evaporation. If the liquid is water based, vapor losses through the surface can be quite extensive. Evaporation can be many times greater than the leakage lost by the seepage into the ground. Even if it is a hydrocarbon liquid, there is still some loss due to evaporation. The present apparatus is a system which includes two separate columns of liquid to expose them to equal surface losses through evaporation. Yet, one of the columns is isolated from the other so that it will lose liquid at a different rate should there be another form of liquid loss in the impoundment. The present apparatus thus provides an indication that the impounded liquid is leaking into the supportive soil. This apparatus is thus very useful in separating the liquid leakage to the ground from the loss due to evaporation from the surface, and by monitoring such leakage versus time, provides information on the rate of such liquid lost to the ground.